Lithium secondary battery

Abstract

To provide a lithium secondary battery having an excellent input and output balance, a high capacity, and a long life. A lithium secondary battery comprising: a positive electrode containing a positive electrode active material which is applied to both sides of a positive electrode collector foil and contains a lithium transition metal complex oxide; a negative electrode containing a negative electrode active material which is applied to both sides of a negative electrode collector foil and occludes and releases lithium; and a nonaqueous electrolytic solution containing a lithium salt, wherein there is an SOC region where a specific input power is almost equal to a specific output power in a range of 20 to 40% of state of charge (SOC) of the lithium secondary battery.

1 . A lithium secondary battery, comprising:
 a positive electrode containing a positive electrode active material which is applied to both sides of a positive electrode collector foil and contains a lithium transition metal complex oxide;   a negative electrode containing a negative electrode active material which is applied to both sides of a negative electrode collector foil and occludes and releases lithium; and   a nonaqueous electrolytic solution containing a lithium salt,   wherein there is an SOC region where a specific input power is almost equal to a specific output power in a range of 20 to 40% of state of charge (SOC) of the lithium secondary battery.   
   
   
       2 . The lithium secondary battery according to  claim 1 , wherein the lithium transition metal complex oxide is represented by a chemical formula LiMO 2  (M is at least one kind of transition metal). 
   
   
       3 . The lithium secondary battery according to  claim 1 , wherein a ratio Ma/Mc between a quantity Mc (mg/cm 2 ) of the positive electrode active material per unit area in one side of the positive electrode collector foil and a quantity Ma (mg/cm 2 ) of the negative electrode active material per unit area in one side of the negative electrode collector foil is in a range of 0.5 to 0.7. 
   
   
       4 . The lithium secondary battery according to  claim 1 , wherein the quantity Mc (mg/cm 2 ) of the positive electrode active material per unit area in one side of the positive electrode collector foil is in a range of 9 to 14 mg/cm 2 . 
   
   
       5 . A lithium secondary battery for a plug-in hybrid electric vehicle, the lithium secondary battery comprising:
 a positive electrode containing a positive electrode active material which is applied to both sides of a positive electrode collector foil and contains a lithium transition metal complex oxide;   a negative electrode containing a negative electrode active material which is applied to both sides of a negative electrode collector foil and occludes and releases lithium; and   a nonaqueous electrolytic solution containing a lithium salt,   wherein there is an SOC region where a specific input power is almost equal to a specific output power in a range of 20 to 40% of state of charge (SOC) of the lithium secondary battery, and   wherein a specific energy is no less than 100 Wh/kg.   
   
   
       6 . The lithium secondary battery for a plug-in hybrid electric vehicle according to  claim 5 , wherein the specific input power and the specific output power that are almost equal to each other in the range of 20 to 40% of state of charge (SOC) are no less than 2000 W/kg. 
   
   
       7 . The lithium secondary battery for a plug-in hybrid electric vehicle according to  claim 5 , wherein the lithium transition metal complex oxide is represented by a chemical formula LiMO 2  (M is at least one kind of transition metal). 
   
   
       8 . The lithium secondary battery for a plug-in hybrid electric vehicle according to  claim 5 , wherein a ratio Ma/Mc between a quantity Mc (mg/cm 2 ) of the positive electrode active material per unit area in one side of the positive electrode collector foil and a quantity Ma (mg/cm 2 ) of the negative electrode active material per unit area in one side of the negative electrode collector foil is in a range of 0.5 to 0.7. 
   
   
       9 . The lithium secondary battery for a plug-in hybrid electric vehicle according to  claim 5 , wherein the quantity Mc (mg/cm 2 ) of the positive electrode active material per unit area in one side of the positive electrode collector foil is in a range of 9 to 14 mg/cm 2 .